Kill command currently has a 5 yard range, and especially if my pet's target is moving I get frequent warning messages that the target is out of range when I try to use Kill Command.

My pet has the speed to keep up with his prey, it's just due to pathing or something that the 5 yard range seems insufficient. Something like 8 yards (pretty standard for caster-centered AoE effects) would probably work a lot better.

We made a couple of fixes to make Kill Command more usable. The pet will no longer check for range or facing since there is already a check in place when the hunter tries to use the ability. This should make Kill Command feel less laggy and should never burn the cooldown or Focus without executing the attack. See how it feels in the next beta or PTR build.